Rapid Colorimetric Antibody Detection Using a Dual-function Peptide Probe for Silver Nanoparticle Aggregation and Antibody Recognition.

Simple and rapid tools for antibody detection are beneficial for therapeutic monoclonal antibody development. Using a synthetic cationic antibody-recognizing peptide, a label-free colorimetric assay for antibody detection was established, in which a solution containing silver nanoparticles (AgNPs) changes color depending on particle aggregation/dispersion. Among the peptide probes we previously screened as IgG binding, one (NKFRGKYK) has four cationic amino acids and a pI of 10.46. Hence, we hypothesized that the peptide would both bind IgG and induce anionic AgNP aggregation via electrostatic interactions. This dual functionality of the IgG binding peptide could be useful for colorimetric detection. The detection of IgG in a solution containing culture media was investigated, and IgG was successfully detected at 100 to 500 nM within 2 min. This method is promising for high-throughput selection of IgG-producing cells since it is fast, readily observable, and does not involve complicated nanoparticle functionalization.